process memory footprints in proc/<pid>/[s|p]maps

Andrew,

Inspired by Matt Mackall's pagemap patches and ideas, these textual interfaces are worked up to achieve the same goals. The patchset runs OK on various read sizes.

1) Add PSS to the existing /proc/<pid>/smaps:
[PATCH 1/4] maps: PSS(proportional set size) accounting in smaps

2) Create /proc/<pid>/pmaps for page granularity mmap footprints:
[PATCH 2/4] maps: address based vma walking
[PATCH 3/4] maps: introduce generic_maps_open()
[PATCH 4/4] maps: /proc/<pid>/pmaps interface - memory maps in granularity of pages

 fs/proc/base.c          |    7 
 fs/proc/internal.h      |    1 
 fs/proc/task_mmu.c      |  354 ++++++++++++++++++++++++++++----------
 fs/seq_file.c           |    1 
 include/linux/proc_fs.h |    6 
 mm/mempolicy.c          |    2 
 6 files changed, 281 insertions(+), 90 deletions(-)

Thank you,
Fengguang